Page 127 - Science Class 07

HOW DOES ELECTRIC CURRENT FLOW?

The flow of electricity through a wire is actually
a flow of electrons. An electron is a nega vely
Flow of
charged subatomic par cle. A wire is a type of water
conductor, a material that electricity easily
travels through.

In electrical conductors, current (flow) results
from the movement of electrons from one
atom to the next. Electrons are either posi vely
or nega vely charged. Nega ve electrons are
Water pump
a racted to posi ve electrons. At the atomic
level, a nega ve electron will jump from one
atom to another. This causes a nega ve
electron to jump from the second atom to a Flow of
third atom. Then one jumps from the third to a water
fourth, and so on. This jumping of nega ve
electrons from atom to atom is electrical flow.
Dry cell
Poten al Difference
In electricity, this difference is known as
Suppose, two vessels with water filled up to poten al difference.
different levels are connected through a pipe.
Thus, if current flows from point A to point B in
Water flows from the higher level to the lower
a wire, we say that A is at a higher poten al
level un l the water levels and hence the water
than B or that there is a poten al difference
pressure, are the same in the two vessels. To
between A and B.
make the water flow con nuously, you need to
connect a water pump to the second vessel, A electric cell or ba ery is a device that can
which constantly pumps up the water to the make current move con nuously in a wire by
first vessel. In this way, the level and hence the crea ng a poten al difference. A cell has two
pressure of water in the first vessel is always terminals—one marked posi ve (+) and the
higher than the second vessel. So, the flow of other marked nega ve (–). The posi ve

water remains con nuous. terminal is at a higher poten al than the
nega ve terminal. When these terminals are
Water flows con nuously because the
connected by a metal wire, current flows from
‘pressure difference’ between the two vessels
the posi ve terminal to the nega ve terminal in
is maintained by the pump.
the wire.
To make electric current flow con nuously, you
ELECTRIC CIRCUIT
need a device that can constantly ‘pump’
current in the same way to create a ‘pressure An electrical circuit is a path or line through
difference’. which an electrical current flows. The path may
be closed (joined at both ends), making it a
loop. A closed circuit makes electrical current
flow possible. It may also be an open circuit

Science-7 127